Module 7: Stoichiometry
Stoichiometry helped the astronauts of Apollo 13 create
scrubbers to filter the air using lithium hydroxide
At first glance, the word "stoichiometry" may seem strange. This word may even be difficult for you to pronounce. Stoichiometry is pronounced stoi-key-om-i-tree. Stoichiometry is the study of the amount of reactants in a reaction compared to the amount of products. Why is this field of chemistry important? At the very least, one might be concerned about the amount of product to expect from a certain amount of reactant. In this module, you will investigate mole ratios, mass to mass stoichiometry, stoichiometric variations, limiting and excess reactants, and percent yield.
Getting Started
Stoichiometry can be a matter of life and death. Did you know that stoichiometry helped to save the astronauts on board the Apollo 13 spacecraft? In 1970, the astronauts of Apollo 13 were supposed to be part of the third mission to land on the Moon. An explosion in one of the oxygen tanks crippled the spacecraft, and the crew was forced to orbit the Moon and return to Earth without landing. Much of their oxygen supply for breathing was lost in the explosion. The crew had to use stoichiometry to figure out how to reuse the oxygen that was already inside of the cabin. As you breathe, you use up oxygen in the air and expel carbon dioxide. High carbon dioxide levels can be fatal. The crew was able to “scrub” the cabin air by reacting it with lithium hydroxide. The crew had to make careful stoichiometric calculations to determine whether the reaction of carbon dioxide and lithium hydroxide would produce enough oxygen to get the entire crew back to Earth. It was a very harrowing trip for the astronauts. Back on Earth, Americans were on the edge of their seats waiting to see if the crew came back alive. It turns out that their careful calculations allowed the astronauts to return back to Earth safely.
Key Vocabulary
To view the definitions for these key vocabulary terms, visit the course glossary.
| actual yield | molarity | stoichiometry |
| Avogadro's Principle | mole ratio | STP |
| excess reactant | percent yield | theoretical yield |
| limiting reactant |